Abstract: A method and associated apparatus for detecting concealed fissile, fissionable or special nuclear material in an article, such as a shipping container, is provided. The article is irradiated with a source of fast neutrons, and fast neutrons released by the fissile or fissionable material, if present, are detected between source neutron pulses. The method uses a neutron detector that can detect and discriminate fast neutrons in the presence of thermal neutrons and gamma radiation. The detector is able to process high count rates and is resistant to radiation damage, and is preferably a solid state neutron detector comprised of silicon carbide.

Abstract: A method of monitoring a nuclear reactor includes monitoring the nuclear reactor with a plurality of radiation sensors having spaced apart attachments to a radiation hard cable; providing signal processing equipment at each end of the cable for processing signals from the radiation sensors; establishing signal time intervals based upon differences in time of arrival of signals from the radiation sensors to the signal processing equipment at each end of the cable; producing a plurality of output signals each of which has an amplitude proportional to a difference in time of arrival of a signal to the signal processing equipment at each end of the cable; and rejecting output signals which have a difference in time of arrival outside of the signal time intervals.

Abstract: A solid state semiconductor neutron detector that automatically varies its sensitivity to provide a pulsed output over the entire range of operation of a nuclear reactor. The sensitivity is varied by changing the thickness or makeup of a converter layer that emits charged particles to the active region of the semiconductor surface.

Abstract: A solid state semiconductor neutron detector that automatically varies its sensitivity to provide a pulsed output over the entire range of operation of a nuclear reactor. The sensitivity is varied by changing the thickness or makeup of a converter layer that emits charged particles to the active region of the semiconductor surface.

Abstract: A method of monitoring a nuclear reactor includes monitoring the nuclear reactor with a plurality of radiation sensors having spaced apart attachments to a radiation hard cable; providing signal processing equipment at each end of the cable for processing signals from the radiation sensors; establishing signal time intervals based upon differences in time of arrival of signals from the radiation sensors to the signal processing equipment at each end of the cable; producing a plurality of output signals each of which has an amplitude proportional to a difference in time of arrival of a signal to the signal processing equipment at each end of the cable; and rejecting output signals which have a difference in time of arrival outside of the signal time intervals.

Abstract: Prompt Gamma Neuteon Activation Analysis (PGNAA) is employed to determined in situ the content of nickel, copper, or other embrittlement-enhancing elements within the weld metal joints of nuclear reactor pressure vessels.

Abstract: Processes for producing stable, radiation hard, highly conductive polymers by a combination of chemical doping and ion irradiation and microelectronics are described. The highly conductive polymers formed by these processes may contain regions of different kinds of conductivity on the same polymer. Resist coatings and masks are used in conjunction with chemical doping and ion irradiation to create specific predetermined n and p conductivity patterns and insulation areas on polymeric films of selected thicknesses for electronic circuitry applications. The resulting circuitry, besides having a conductivity approaching that of metal, is extremely light in weight, flexible, and conductively stable. Several different configurations of microelectronic junction devices fabricated from single type or multiple type conductivity polymer films used either alone or with a polymer of opposite conductivity and a suitable metal or metals are disclosed.

Abstract: An apparatus is provided for determining the thermal history of an environment for purposes of monitoring thermal aging in equipment or the extent to which a process has proceeded. The apparatus comprises a plurality of solid state track recorders, and the range of activation energy values among the solid state track recorders encompasses the activation energy of the thermal aging process of the equipment to be monitored. Using Arrhenius functions, data obtained from the apparatus can be used to determine an equivalent average temperature which is combined with the equipment life data to determine the extent of thermal aging.

Abstract: A method for producing ultralow-mass fissionable deposits for nuclear reactor dosimetry is described, including the steps of holding a radioactive parent until the radioactive parent reaches secular equilibrium with a daughter isotope, chemically separating the daughter from the parent, electroplating the daughter on a suitable substrate, and holding the electroplated daughter until the daughter decays to the fissionable deposit.

Abstract: A method is described for detecting and correcting for isotope burn-in during-long term neutron dosimetry exposure. In one embodiment, duplicate pairs of solid state track recorder fissionable deposits are used, including a first, fissionable deposit of lower mass to quantify the number of fissions occuring during the exposure, and a second deposit of higher mass to quantify the number of atoms of for instance .sup.239 Pu by alpha counting. In a second embodiment, only one solid state track recorder fissionable deposit is used and the resulting higher track densities are counted with a scanning electron microscope. This method is also applicable to other burn-in interferences, e.g., .sup.233 U in .sup.232 Th or .sup.238 Pu in .sup.237 Np.

Abstract: An alpha recoil ion-implantation method and apparatus are described which use an alpha-emitting source that is a radioactive parent of the daughter isotope of interest to implant into a suitable substrate the recoil daughter ions resulting from alpha decay of the parent. For example, a .sup.241 Am source in thin layer form is placed next to a substrate such as a solid state track recorder in a vacuum which houses an assembly for rotating opposing disks receiving the alpha-emitting source and the substrate, respectively. Each alpha decay of .sup.241 Am results in a .sup.237 Np ion with enough recoil energy to be implanted into the substrate. Fissionable deposits of .sup.239 Pu, .sup.235 U, and .sup.238 U can also be made by this method and apparatus.

Abstract: A method and apparatus are described for producing a high fluence neutron dosimeter which serves as a permanent record for fission rate measurement. An alpha-emitting source which is a radioactive parent of the daughter isotope of interest is used to implant recoil ions resulting from alpha decay into a substrate such as a mica solid state track recorder. The source and the mica solid state track recorder are arranged in spaced, opposing relation in an assembly housed in a vacuum. For example, a .sup.241 Am source in thin layer form can be placed next to the mica solid state track recorder. Each alpha decay of .sup.241 Am results in a .sup.237 Np ion with enough recoil energy to be implanted in the solid state track recorder. An ion-implanted mica solid state track recorder so produced is then exposed to neutrons, etched, and both the induced fission tracks and recoil ion tracks are counted. As a result, the fission rate in fissions per atom can be calculated.

Abstract: A high fluence neutron dosimetry method is described, including the steps of: exposing a dosimeter containing an alpha-emitting target isotope to neutron irradiation to form an alpha-emitting product isotope; determining the alpha decay rates of the target nucleus and the product nucleus; and using known alpha decay constants for the target nucleus and the product nucleus and the determined alpha decay rates of the target nucleus and the product nucleus to determine the neutron capture rate of the product nucleus.